Automatic adjusting device for output power

ABSTRACT

An automatic adjusting device is provided, which is used for adjusting an output power of a power supply and comprises an automatic adjusting circuit. The automatic adjusting circuit includes a comparing unit and a programmable signal generating unit. The comparing unit compares a limiting level and a protection level and produces a comparison signal. The protection level limits the output power provided by the power supply. The programmable signal generating unit generates the protection level and adjusts the protection level according to the comparison signal for adjusting the output power. The programmable signal generating unit will adjust the protection level according to the limiting level. Thereby, the output power can be adjusted automatically without manual adjustment. Consequently, the cost can be reduced and the adjusting accuracy can enhanced.

REFERENCE TO RELATED APPLICATION

This Application is based on Provisional Application Ser. No.61/641,366, filed 2 May 2012, currently pending.

FIELD OF THE INVENTION

The present invention relates generally to an automatic adjustingdevice, and particularly to an automatic adjusting device for outputpower.

BACKGROUND OF THE INVENTION

Power supplies provide power required by electronic devices. Dependingon the circuit structure, there are linear power supplies and switchingpower supplies. Power supplies are extensively applied to various fieldssuch as mobile communication devices, personal digital assistants,computer and peripheral equipment, servers, and network equipment.Thereby, power supplies power supplier play a crucial role in electronicdevices.

The protection mechanism in the control circuit of a power supplyprovides very important functions, such as over-voltage, over-current,over-power, and low-voltage protection, for normal operations andpreventing damages. Once the situation of overload, short circuit, orlow voltage occurs, the power supply with complete protection mechanismwill stop supplying the output power for avoiding damages on internaldevices or relevant equipment. In other words, the protection mechanismis used for limiting the output power of the power supply. In general,there is a protection level inside the power supply. When the voltage orcurrent exceeds the protection level, it is regarded that the situationof over voltage, over current, or over power occurs. At this time, thepower supply is shut off for protecting the power supply and the otherrelevant equipment.

Nonetheless, the protection levels among different batches of powersupplies differ due to the accumulation of production errors in circuitdevices such as resistors, inductors, or capacitors. As a result, thereare differences in the output power among different batches of powersupplies. For solving this problem, generally, a variable resistor isfurther disposed in the power supply. By adjusting the resistance of thevariable resistor manually, the protection level is adjusted.Consequently, the labor cost is increased. Besides, after long-termusage, the variable resistor will chap or fall off and varying theprotection level, which, in turn, leads to inaccuracy in the limitinglevel of the output power. At worst, the power supply might be evendamaged.

FIG. 1 shows a production flowchart of the power supply according to theprior art. Because a variable resistor is required in the power supplyaccording to the prior art for adjusting the protection level, in theproduction process, the step S1 is first performed for disposing thevariable resistor in the circuit by manual insertion. Afterwards, thestep S2 is performed for soldering the variable resistor on the circuitby using a tin furnace. Then, the step S3 is performed for initializingthe power supply, which includes testing and tuning on the stability ofthe power supply and adjustment for over voltage and over current. Theadjustment described above is to adjust the resistance of the variableresistor manually. Next, the steps S4 is executed for performingburn-in. afterwards, the step S5 is performed for the hi-pot test. Then,the step S6 is performed for the protection test. Next, the step S7 isperformed for the function test. Finally, the step S8 is performed forthe power test.

It is known form the above that in the power supply according to theprior art, a variable resistor is required. By adjusting the resistanceof the variable resistor, the protection level is adjusted, which, inturn, adjusts the output power of the power supply. This method isextremely labor intensive and thus leading to increase in cost. Inaddition, because the variable resistor in the circuit is vulnerable todamages or aging due to external factors such as humidity andtemperature, the resistance may vary and thereby altering the protectionlevel. Consequently, errors in the protection level from the initialsetup may occur, and hence influencing the output power of the powersupply.

Accordingly, the present invention provides an automatic adjustingdevice for solving the problems described above. According to thepresent invention, the protection level can be adjusted automaticallyand thus fixing the level of the output power to the expected limitswithout using the variable resistor and adjusting the protection levelmanually. Thereby, the problems in the prior art as described above canbe solved.

SUMMARY

An objective of the present invention is to provide an automaticadjusting device for output power. The automatic adjusting deviceaccording to the present invention has a programmable signal generatingunit for generating the protection level. The protection level isadjusted according to the difference between a limiting level and theprotection level for adjusting the output power automatically. Withoutextra labor, the cost can be reduced and the adjusting accuracy isenhanced.

The present invention discloses an automatic adjusting device for outputpower, which is used for adjusting an output power of a power supply andcomprises an automatic adjusting circuit. The automatic adjustingcircuit includes a comparing unit and a programmable signal generatingunit. The comparing unit compares a limiting level and a protectionlevel and produces a comparison signal. The protection level limits theoutput power provided by the power supply. The programmable signalgenerating unit generates the protection level and adjusts theprotection level according to the comparison signal for adjusting theoutput power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a production flowchart of the power supply according to theprior art;

FIG. 2 shows a circuit diagram of the power supply according to anembodiment of the present invention;

FIG. 3 shows a circuit diagram of the protection chip according to anembodiment of the present invention;

FIG. 4 shows wave diagrams of the power supply operating normallyaccording to the present invention;

FIG. 5 shows wave diagrams of the protection chip executing over-voltageprotection according to the present invention;

FIG. 6 shows wave diagrams of the protection chip executing over-currentprotection according to the present invention;

FIG. 7 shows a circuit diagram of the programmable signal generatingunit according to the present invention;

FIG. 8A shows a connection diagram of the power supply, the testingmodule, and the control module according to an embodiment of the presentinvention;

FIG. 8B shows a block diagram of the power supply, the testing module,and the control module according to an embodiment of the presentinvention; and

FIG. 9 shows wave diagrams of an automatic adjusting device according tothe present invention.

DETAILED DESCRIPTION

In order to make the structure and characteristics as well as theeffectiveness of the present invention to be further understood andrecognized, the detailed description of the present invention isprovided as follows along with embodiments and accompanying figures.

FIG. 2 shows a circuit diagram of the power supply according to anembodiment of the present invention. As shown in the figure, the powersupply 10 according to the present invention comprises a bridgerectifier 101, a plurality of capacitors 102, 110, an inductor 109, apower transistor 104, a resistor 105, a plurality of diodes 107, 108, acontroller 106, and a transformer 103 having a primary side and asecondary side. The primary side includes a primary winding N_(P), andthe secondary side includes a secondary winding N_(S). One terminal ofthe capacitor 102 is coupled to an output of the bridge rectifier 101and one terminal of the primary winding N_(P); the other terminal of thecapacitor 102 is coupled to a ground. The bridge rectifier 101 rectifiesan input power AC to a DC voltage. The capacitor 102 filters the DCvoltage, produces a DC input voltage V_(IN), and supplies the DC inputvoltage V_(IN) to the primary winding N_(P).

The power transistor 104 is used for switching the transformer 103 andthus controlling the conversion of the energy from the primary windingN_(P) of the transformer 103 to the secondary winding N_(S). A draw ofthe power transistor 104 is connected in series with the other terminalof the primary winding N_(P). The controller 106 is coupled to a gate ofthe power transistor 104. The controller 106 produces a switching signalPWM and outputs the switching signal PWM to the power transistor 104 forcontrolling the power transistor 104 and switching the transformer 103.The resistor 105 is coupled between a source of the power transistor 104and the ground. A switching current I_(P) of the transformer 103 flowsthrough the resistor 105 and produces a current sensing signal V_(CS) atthe resistor 105. The current sensing signal V_(CS) is transmitted tothe controller 106, which produces the switching signal PWM according tothe current sensing signal V_(CS) and a feedback signal (not shown inthe figure). The feedback signal is related to the loading status of thepower supply 10. The method for producing the feedback signal is wellknown to a person having ordinary skill in the art. Hence, the detailswill not be described here. The anodes of the diodes 107, 108 arecoupled to both terminals of the secondary winding N_(S) of thetransformer 103, respectively. A terminal of the inductor 109 is coupledto the cathodes of the diodes 107, 108. The other terminal of theinductor 109 is coupled to the output of the power supply 10. Thecapacitor 110 is coupled between the output of the power supply 10 andthe ground and thus producing the output power, which is the outputvoltage V_(OUT) or the output current I_(OUT).

Refer again to FIG. 2. The automatic adjusting device according to thepresent invention is used for adjusting the output power of the powersupply 10 such as adjusting a maximum level of the output voltageV_(OUT) or the output current I_(OUT). The automatic adjusting deviceaccording to the present invention comprises an automatic adjustingcircuit 70 and a test load 301. The automatic adjusting circuit 70includes a sensing device R_(SENSE), an impedance device R_(IS), and aprotection chip 701. The sensing device R_(SENSE) is coupled between theoutput and the test load 301. The test load 301 is coupled to the outputof the power supply 10 by way of the sensing device R_(SENSE) and drawsthe output power. The test load 301 is used during the tuning andadjusting period for adjusting the output power of the power supply 10.Under normal operations, there is no test load 301 coupled to the powersupply 10. Instead, the power supply 10 is coupled to the output load.The sensing device R_(SENSE) produces a sensing signal VS according tothe output power supplied to the test load 301 and the sensing signal VSis related to the state of the output power of the power supply 10.According to the present embodiment, the sensing signal VS is determinedby the impedance of the sensing device R_(SENSE) and the amplitude ofthe output current I_(OUT). In the present invention, when the automaticadjusting device adjusts the output power of the power supply 10, thesensing signal VS is used as a limiting level.

The impedance device R_(IS) is coupled between the output of the powersupply 10 and the protection chip 701 for producing a protection levelIS and providing the protection level IS to the protection chip 701. Theprotection level IS limits the output power provided by the power supply10, The protection chip 701 is coupled to the impedance device R_(IS)and the sensing device R_(SENSE). When the automatic adjusting deviceadjusts the output power of the power supply 10, the protection chip 701compare the sensing signal VS with the protection level IS and adjuststhe output power according to the comparison result. The details ofadjusting the output power will be described later. In addition, acapacitor C_(S) is coupled between the impedance device R_(IS) and thesensing device R_(SENSE) for suppressing noises.

The protection chip 701 is coupled to the output of the power supply 10.When the power supply 10 is used normally, the protection chip 701judges if over voltage, low voltage, or over current occurs according tothe sensing signal VS and the protection level IS. When over voltage,low voltage, or over current occurs in the power supply 10. theprotection chip 701 produces a protection signal FPOB and transmits theprotection signal FPOB to the controller 106 for driving the controlling106 to disable the power supply 10. According an embodiment, anoptocoupler 111 is coupled between the protection chip 107 and thecontroller 106. The protection signal FPOB is transmitted to thecontroller 106 by way of the controller 106. Besides, a resistor R₁ iscoupled between the optocoupler 111 and a supply voltage V_(CC).

The protection chip 701 receives an activation signal PSONB and disablesthe protection signal FPOB according to the activation signal PSONB foractivating the power supply 10. Moreover, the protection chip 701 isfurther coupled to the connection point between the diodes 107, 108 ofthe power supply 10 for receiving a detecting voltage V_(DET). By usingthe detecting voltage V_(DET) as a power good input (PGI) signal, thestate of the output power of the power supply 10 can be detected. Theprotection chip 701 produces a power good output (PGO) signal accordingto the PGI signal. The PGO signal is used for indicating if the outputpower of the power supply 1 is normal. Thereby. the PGO signal isequivalent to a confirmation signal. A resistor R₂ is coupled betweenthe supply voltage V_(CC) and the protection chip 701 for producing thePGO signal.

When the state of the output power of the power supply 10 is normal, theprotection chip 701 enables the PGO signal according to the PGI signal.As the automatic adjusting device adjusts the output power of the powersupply 10, the protection chip 701 will adjust the output powerautomatically according to the activation signal PSONB and the PGOsignal. At this moment, the protection chip 701 will transmit the PGOsignal to the test load 301. Upon receiving the PGO signal, the testload 301 will start to draw the output power for performing automaticadjusting of the output power.

FIG. 3 shows a circuit diagram of the protection chip according to anembodiment of the present invention. As shown in the figure, theprotection chip 701 includes a plurality of comparing units 7016, 7017,7018, 7019, a flip-flop 7020, an adjusting unit 7011, a programmablesignal generating unit 7012, a plurality of debounce circuits DB1, DB2,a plurality of delay circuits DL1, DL2, DL3, DL4, a plurality of ORgates OR1, OR2, OR3, a NOR gate NOR, an AND gate AND, and a plurality oftransistors 7021, 7022.

The debounce circuit DB2 receives the activation signal PSONB. As thelevel of the activation signal PSONB is changed from high to low andmaintained for a time T4, the debounce circuit DB2 outputs a low outputsignal for activating the power supply 10. In other words, when thelevel of the activation signal PSONB is maintained low, the debouncecircuit DB2 does not output the activation signal PSONB until after thedelay time T4. The debounce circuit DB2 is used for eliminating thedebouncing phenomena. Thereby, false activation of the power supply 10due to a transient low level of the activation signal PSONB caused bynoises or external factors can be avoided.

An input of the NOR gate NOR is coupled to an output of the debouncecircuit DB2 for receiving the output signal of the debounce circuit DB2.An output of the NOR gate NOR is coupled to gate of the transistor 7021for controlling the transistor 7021. A source of the transistor 7021 iscoupled to the ground. A draw of the transistor 7021 is coupled to theoptocoupler 111, as shown in FIG. 2, for producing the protection signalFPOB. When the level of the output signal of the debounce circuit DB2 islow, the level of the output signal of the NOR gate NOR is high andhence turning on the transistor 7021. Thereby, the level of theprotection signal FPOB is low, which means that the power supply 10 isnormal. Then the controller 106, as shown in FIG. 2, will activate thepower supply 10. In addition, the output of the debounce circuit DB2 isfurther coupled to a reset R of the flip-flop 7020 and a non-inverseinput of the OR gate OR3. The output of the NOR gate NOR is furthercoupled to an inverse input of the OR gate OR3.

A positive input of the comparing unit 7019 receives the PGI signal anda negative input thereof receives a reference level Vref1. The comparingunit 7019 compares the PGI signal with the reference level Vref1 andoutputs a comparison signal. The delay circuit DL 4 is coupled betweenan output of the comparing unit 7019 and an inverse input of the OR gateOR3 and receives the comparison signal of the comparing unit 7019. Whenthe level of the PGI signal is higher than the reference level Vref1,the level of the comparison signal of the comparing unit 7019 is changedfrom low to high. After the level of the comparison signal of thecomparing unit 7019 is high and maintained for a time T8, the delaycircuit DL4 output a high output signal. Namely, the delay circuit DL4does not output the comparison signal of the comparing unit 7019 untildelayed for the time T8, which means that the output power of the powersupply 10 is normal. The delay circuit DL4 is used for confirming thestate of the PGI signal. Thereby, false judgment of the state of theoutput power of the power supply 10 due to transient variations of thePGI signal caused by noises or external factors can be avoided.

An output of the OR gate OR3 is coupled to a gate of the transistor7022; a source of the transistor 7022 is coupled to the ground; a drawof the transistor 7022 is coupled to the resistor R₂, as shown in FIG.2. for producing the PGO signal. As the level of the output signal ofthe delay circuit DL4 is high, the level of the output signal of the ORgate OR3 is low and thus cutting off the transistor 7022. Consequently,the level of the PGO signal is pulled high by the supply voltage V_(CC),as shown in FIG. 2. Then it means that the output power of the powersupply 10 is normal.

Besides, when the level of the PGI signal is lower than the referencesignal Vref1, the level of the comparison signal of the comparing unit7019 is changed from high to low. When the level of the comparisonsignal of the comparing unit 7019 is changed to low, the delay circuitDL4 does not output the comparison signal of the comparing unit 7019until after the delay time T6. Then it means that the output power ofthe power supply 10 is abnormal. As the output signal of the delaycircuit DL4 is low, the level of the output signal of the OR gate OR3 ishigh and hence turning on the transistor 7022. Thereby, the level of thePGO signal is low, meaning that the output power of the power supply 10is abnormal.

Moreover, the output of the comparing unit 7019 is further coupled to aninput of the delay circuit DL3. An output of the delay circuit DL3 iscoupled to an input of the AND gate AND. After the level of thecomparison signal of the comparing unit 7019 is maintained for a timeT5, the delay circuit DL3 outputs the comparison signal of the comparingunit 7019 to the AND gate AND.

FIG. 4 shows wave diagrams of the power supply operating normallyaccording to the present invention. As shown in the figure, as the levelof the activation signal PSONB is low, it means to activate the powersupply 10. The activation signal PSONB is delayed for the time T4 by thedebounce circuit DB2. Then the low-level activation signal PSONB istransmitted to the NOR gate NOR and turning on the transistor 7021.Thereby, the protection signal FPOB is disabled for activating the powersupply 10. After the power supply 10 is activated, the output power willbe generated, and hence the detecting voltage V_(DET) at the output ofthe power supply 10, as shown in FIG. 2. will increase. In other words,the level of the PGI signal will increase as well and will be greaterthan the reference level Vref1. Thereby, the level of the comparisonsignal of the comparing unit 7019 is high. After the delay time T8, thedelay circuit DL4 will output the comparison signal of the comparingunit 7019 to the inverse-input of the OR gate OR3 for cutting off thetransistor 7022. Accordingly, the level of the PGO signal is high, whichmeans that the output power of the power supply is normal.

If the power supply 10 has problems, the detecting voltage V_(DET) atthe output of the power supply 10 will be reduced. In other words, thelevel of the PGI signal will be reduced as well and becoming smallerthan the reference level Vref1. Then the level of the comparison signalof the comparing unit 7019 is low. It is output to the OR gate OR3 afterbeing delayed for the time T6 by the delay circuit DL4. The level of theoutput signal of the OR gate OR3 is high and hence turning on thetransistor 7022. Thereby, the level of the PGO signal is low, whichmeans that the output power of the power supply 10 is abnormal.

Refer again to FIG. 3. As the power supply 10 is operating, theprotection chip 701 receives the sensing signal VS and the protectionlevel IS for sensing the state of the output power of the power supply10 and judging if over voltage, low voltage, or over current occurs. Apositive input of the comparing unit 7016 receives the sensing signalVS; a negative input thereof receives a reference level Vref2 andcompares the sensing signal VS with the reference level Vref2. Thedebounce circuit DB1 is coupled between an output of the comparing unit7016 and an input of the OR gate OR2. The input of the OR gate OR2receives the output signal of the debounce circuit DB1. An output of theOR gate OR2 is coupled to an input J of the flip-flop 7020; an output Qof the flip-lop 7020 is coupled to the other input of the NOR gate NOR.The flip-flop 7020 outputs signal to the NOR gate NOR according theoutput signal of the OR gate OR2. Besides, an input K of the flip-flop7020 is coupled to the ground.

When the sensing signal VS is higher than the reference level Vref2, thelevel of the comparison signal output by the comparing unit 7016 ishigh. After the high-level comparison signal of the comparing unit 7016is maintained for a time T2, the debounce circuit DB1 output ahigh-level output signal, meaning that over voltage occurs. When thelevel of the output signal of the debounce circuit DB1 is high, thelevel of the output signal of the OR gate OR2 is high, and the level ofthe output signal of the flip-flop 7020 is high as well. Thereby, theNOR gate NOR will cut off the transistor 7021, making the level of theprotection signal FPOB high and meaning that the power supply 10 isabnormal. The protection signal FPOB is transmitted to the controller106, as shown in FIG. 2. The controller 106 disables the switchingsignal PWM according to the protection signal FPOB for disabling thepower supply 10.

FIG. 5 shows wave diagrams of the protection chip executing over-voltageprotection according to the present invention. As shown in the figure,as the level of the PGI signal increases and becomes greater than thereference level Vref1, after the delay time T8 delayed by the delaycircuit DL4, the level of the PGO signal is high. When the level of thesensing signal VS is higher than the reference level Vref2, the level ofthe comparison signal of the comparing unit 7016 is high. The comparisonsignal will be delayed for the time T2 by the debounce circuit DB1. Thenthe high-level comparison signal of the comparing unit 7016 will betransmitted to the OR gate OR2, which will output a high-level signal tothe flip-flop 7020. Thereby, the flip-flop 7020 will drive the NOR gateNOR to output a low-level output signal for cutting off the transistor7021. Accordingly, the protection signal FPOB is enabled for shuttingoff the power supply 10. At this time, the levels of the sensing signalVS and the PGI signal will be low because the power supply 10 is shutoff.

Refer again to FIG. 3. A negative input of the comparing unit 7017receives the sensing signal VS; a positive thereof receives a referencelevel Vref3 and compares the sensing signal VS with the reference levelVref3 for outputting a comparison signal. An input of the delay circuitDL1 is coupled to an output of the comparing unit 7017 and receives thecomparison signal of the comparing unit 7017. An output of the delaycircuit DL1 is coupled to an input of the OR gate OR1. An output of theOR gate OR1 is coupled to the other input of the AND gate AND. An outputof the AND gate AND is coupled to the other input of the OR gate OR2. Asthe sensing signal VS is lower than the reference level Vref3, the levelof the comparison signal of the comparing unit 7017 is high. When thecomparison signal of the comparing unit 7017 is high and maintained fora time T1, the delay circuit DL1 output a high-level output signal,which means that low voltage occurs. When the level of the output signalof the delay circuit DL1 is high, the level of the output signal of theOR gate OR1 is high and the output signal of the OR gate OR1 is outputto the AND gate AND.

When the levels of output signals of the delay circuits DL1, DL3 areboth high, the level of the output signal of the AND gate AND is alsohigh and the output signal of the AND gate AND is transmitted to the ORgate OR2. At this time, the level of the output signal of the OR gateOR2 is high and the level of the output signal of the flip-lop 7020 isalso high. Thereby, the NOR gate NOR will cut off the transistor 7021,which makes the level of the protection signal FPOB high, meaning thatthe power supply 10 is abnormal. The controller 106, as shown in FIG. 2,will disable the switching signal PWM according to the protection signalFPOB for disabling the power supply 10.

The programmable signal generating unit 7012 is coupled to the impedancedevice R_(IS), as shown in FIG. 2, and a positive input of the comparingunit 7018. The programmable signal generating unit 7012 is used forgenerating the protection level IS. According to an embodiment of thepresent invention, the programmable signal generating unit 7012 is aprogrammable current source, which provides a programmable current forgenerating the protection level IS. The amplitude of the programmablecurrent and the impedance of the impedance device R_(IS) determine theamplitude of the protection level IS.

A negative input of the comparing unit 7018 receives the sensing signalVS; the positive input thereof receives the protection level IS andcompares the sensing signal VS with the protection level IS foroutputting a comparison signal. An input of the delay circuit DL2 iscoupled to an output of the comparing unit 7018. An output of the delaycircuit DL2 is coupled to an output of the OR gate OR1. When the sensingsignal VS is lower than the protection level IS, the level of thecomparison signal of the comparing unit 7018 is high. As the level ofthe comparison signal of the comparing unit 7018 is high and maintainedfor a time T3, the delay circuit DL2 outputs a high-level output signal,which means that the output current I_(OUT) is too large, as shown inFIG. 2, and over current occurs. When the level of the output signal ofthe delay circuit DL2 is high, the level of the output signal of the ORgate OR1 is also high and the output signal is output to the AND gateAND.

When the levels of the output signals of the delay circuits DL2, DL3 areboth high, the level of the output signal of the AND gate AND will alsobe high. At this time, the level of the output signal of the OR gate OR2is high. Thereby, the level of the output signal of the flip-flop 7020is also high. Then, the NOR gate NOR will cut off the transistor 7021and enable the protection signal FPOB for disabling the power supply 10.

FIG. 6 shows wave diagrams of the protection chip executing over-currentprotection according to the present invention. As shown in the figure,when the power supply 10 is operating normally, the sensing signal VS ishigher than the protection level IS. As over current occurs, the sensingsignal VS will be lower than the protection level IS; the comparing unit7018 will output a high-level comparison signal. After the delay time T3by the delay circuit DL2, this comparison signal is transmitted to theOR gate OR1 so that the OR gate OR1 outputs a high-level output signalto the OR gate OR2. The level of the output signal of the OR gate OR2becomes high and the output signal is transmitted to the NOR gate NORvia the flip-flop 7020. Then the level of the output signal of the NORgate NOR is low, which cuts off the transistor 7021 for enabling theprotection signal FPOB and thus further shutting off the power supply10.

Refer again to FIG. 3. The adjusting unit 7011 is coupled to the outputof the comparing unit 701 and the programmable signal generating unit7012. When the automatic adjusting device adjusts the output power ofthe power supply 10, the adjusting unit 7011 will produce an adjustingsignal ADS_(0−n) according to the comparison signal of the comparingunit 7018 for adjusting the level of the programmable current of theprogrammable signal generating unit 7012 and hence adjusting theprotection level IS. Consequently, the maximum level of the output powercan be adjusted. According to the present embodiment, adjusting theprotection level IS can adjust the maximum level of the output currentI_(OUT). Accordingly, the programmable signal generating unit 7012 willadjust the protection level IS according to the comparison signal of thecomparing unit 7018 for adjusting the output power.

In addition, the adjusting unit 7011 further receives the activationsignal PSONB and the PGO signal and is controlled by the activationsignal PSONB and the PGO signal. When the waveform of the activationsignal PSONB is a specific waveform and the level of the PGO signal ishigh, the adjusting unit 7011 will produce the adjusting signalADS_(0−n) according to the comparison signal of the comparing unit 7018for controlling the programmable signal generating unit 7012 to adjustthe protection level IS. Thereby, the maximum level of the output powercan be adjusted.

The specific waveform described above is shown in FIG. 9. The activationsignal PSONB has three pulses. The width of the first pulse is largerthan the width of the second and of the third. It is know that thisspecific waveform is different from the waveform of the activationsignal PSONB in FIG. 4. When the adjusting unit 7011 receives theactivation signal PSONB having the specific waveform and the high-levelPGO signal, it will produce the adjusting signal ADS_(0-n) according tothe comparison signal of the comparing unit 7018. In other words, whenthe power supply 10 is operating normally and the activation signal hasno specific waveform, the adjusting unit 7011 will not adjust theprotection level IS. The specific waveform described above is only anembodiment of the present invention; the specific waveform according tothe present invention is not limited to the one according to presentembodiment. The PGO signal according to the present invention is used asa confirmation signal for making sure that the power supply 10 isnormal. According to the present invention, another signal can also beused as the confirmation signal. Thereby, the adjusting unit 7011 canalso adjust the protection level IS according to another signal and theactivation signal PSONB having a specific waveform.

FIG. 7 shows a circuit diagram of the programmable signal generatingunit according to the present invention. As shown in the figure, theprogrammable signal generating unit 7012 includes a current source unit7014, a switching unit 7015. The switching unit 7015 includes aplurality of switches SW₀-SW_(n) turned on or off according to theadjusting signals ADS₀-ADS_(n), respectively. The current source unit7014 includes a plurality of current sources I₀-I_(n) for providing aplurality of currents and producing the programmable currents. Thecurrent sources I₀-I_(n) are coupled to the plurality of switchesSW₀-SW_(n) of the switching unit 7015, respectively. The adjustingsignals ADS₀-ADS_(n) are used for turning on or off the plurality ofswitches SW₀-SW_(n) for controlling the currents of plurality of currentsources I₀-I_(n). When the plurality of switches SW₀-SW_(n) are turnedon, the currents of the plurality of current sources I₀-I_(n) flow tothe ground. Thereby, the programmable signal generating unit 7012switches the plurality of switches SW₀-SW_(n) according to the adjustingsignals ADS_(0-n). Then, the levels of the programmable currents can beadjusted. The protection level IS is adjusted accordingly.

Refer again to FIG. 2. When the automatic adjusting device adjusts theoutput power of the power supply 10, the test load 301 will be coupledto the output of the power supply 10 for drawing the output power. Whenthe power supply 10 is turned on and provides the output power normally,the level of the PGO signal is high. The output power is output to thetest load 301. At this time, the test load 301 will draw the outputpower according to a set value, for example, drawing 20 amperes ofoutput current I_(OUT). Thereby, the output power provided to the testload 301 corresponds to the set value. This set value is just the setmaximum value of the output power for the power supply 10. Then, thesensing signal VS pertinent to the output power is used as the limitinglevel and adopted as the reference level for adjusting the protectionlevel IS and the output power.

Please refer to FIG. 3. When the automatic adjusting device adjusts theoutput power of the power supply 10, the adjusting unit 7011 willcontrol the programmable signal generating unit 7012 for adjusting theamplitude of the programmable current of the programmable signalgenerating unit 7012 and adjusting the protection level IS. Then theprotection level IS is equivalent to the sensing signal VS. Accordingly,the maximum level of the output power can be adjusted. Besides, theadjusting unit 7011 and the programmable signal generating unit 7012according to the present invention can also be applied to the comparingunits 7016, 7017 for producing the reference levels Vref2, Vref3, whichare used as the protection levels. Thereby, the maximum and the minimumvalues of the output voltage can be adjusted as well.

FIGS. 8A, 8B, and 9 show a connection diagram, a block diagram, and wavediagrams of the power supply, the testing module, and the control moduleaccording to an embodiment of the present invention. The automatictesting device according to the present invention can be applieddirectly to the automatic test equipment (ATE). The automatic adjustingdevice according to the present invention further comprises a testingmodule 30 and a control module 50. The testing module 30 is disposed inthe ATE for producing a testing signal TTL and providing the input powerAC to the power supply 10. The power supply 10 provides a supply powerVsb to the control module 50 according to the input power AC and thesupply power Vsb is used as the input power VCC of the control module50. The control module 50 outputs the activation signal PSONB having thespecific waveform to the power supply 10 according to the testing signalTTL.

When the protection chip 701 of the power supply 10 receives theactivation signal PSONB, as shown in FIG. 2, after the time T4, theprotection signal FPOB is disabled. The power supply 10 is activated andthe output power is supplied. Then after the time T8, the protectionchip 701 enables the PGO signal. After the testing module 30 receivesthe high-level PGO signal, the test load 301 in the testing module 30,as shown in FIG. 2, starts to draw the output power according to the setvalue for producing the sensing signal VS and the limiting level. Whenthe PGO signal is established, the protection chip 701 performsautomatic adjusting according to the activation signal PSONB and the PGOsignal.

Furthermore, as shown in FIG. 8A, the control module 50 has a connector41; the testing module 30 has a connector 43. The control module 50outputs the activation signal PSONB to the testing module 30 via theconnectors 30, 43. The connector 43 is connected electrically with aconnector 21. Thereby, the connector 43 transmits the activation signalPSONB to the connector 21. Then, through the connector 21, theactivation signal PSONB is transmitted to a connector 23 of the powersupply 10 and thus controlling the power supply to adjust automatically.

To sum up, the automatic adjusting device for output power according tothe present invention is used for adjusting the output power of a powersupply. The automatic adjusting device uses the programmable signalgenerating unit to adjust the protection level and thereby adjusting theoutput power automatically. Without using variable resistors, no manualadjustment of the resistance of the variable resistors for adjusting theoutput power is required. Hence, the problem of intensive use of laborcan be solved. In addition, the programmable signal generating unit canbe disposed in the protection chip and thus avoiding damages. Thereby,the present invention can improve the accuracy of adjusting the outputpower.

Accordingly, the present invention conforms to the legal requirementsowing to its novelty, nonobviousness, and utility. However, theforegoing description is only embodiments of the present invention, notused to limit the scope and range of the present invention. Thoseequivalent changes or modifications made according to the shape,structure, feature, or spirit described in the claims of the presentinvention are included in the appended claims of the present invention.

1. An automatic adjusting device used for adjusting an output power of apower supply, comprising an automatic adjusting circuit, and saidautomatic adjusting circuit including: a comparing unit, comparing alimiting level and a protection level for producing a comparison signal,and said protection level limiting said output power provided by saidpower supply; and a programmable signal generating unit, generating saidprotection level, and adjusting said protection level according to saidcomparison signal for adjusting said output power.
 2. The automaticadjusting device as claimed in claim 1, further comprising a test loadcoupled to said power supply, said test load drawing said output poweraccording to a set value for producing said limiting level, and thelevel of said output power provided to said test load by said powersupply corresponding to said set value.
 3. The automatic adjustingdevice as claimed in claim 2, wherein said automatic adjusting circuitfurther includes a sensing device coupled to said comparing unit and anoutput of said power supply, said sensing device produces said limitinglevel according to the level of said output power provided to said testload by said power supply.
 4. The automatic adjusting device as claimedin claim 1, wherein said automatic adjusting circuit further includes anadjusting unit producing an adjusting signal according to saidcomparison signal for controlling said programmable signal generatingunit to adjust said protection level.
 5. The automatic adjusting deviceas claimed in claim 1, wherein said programmable signal generating unitis a programmable current source, and said automatic adjusting circuitfurther includes a impedance device coupled to an output of said powersupply and said output power, said programmable current source iscoupled to said impedance device and said comparing unit; saidprogrammable current source provides a programmable current and producessaid protection level; said protection level is determined by the levelof said programmable current and the impedance of said impedance device;and said comparison signal adjusts the level of said programmablecurrent for adjusting said protection level.
 6. The automatic adjustingdevice as claimed in claim 1, wherein said comparing unit and saidprogrammable signal generating unit are integrated in a protection chipof said power supply.
 7. The automatic adjusting device as claimed inclaim 1, wherein said limiting level corresponds to a set value, andsaid programmable signal generating unit adjusts said protection levelaccording to said comparison signal.
 8. The automatic adjusting deviceas claimed in claim 1, wherein said protection level limits a maximumlevel of said output power provided by said power supply, and saidprogrammable signal generating unit adjusts said protection levelaccording to said comparison signal for adjusting said maximum level ofsaid output power.
 9. The automatic adjusting device as claimed in claim1, further comprising: a testing module, producing a testing signal andproviding an input power to said power supply; and a control module,producing an activation signal according to said testing signal; whereinsaid power supply receives said input power and provides said outputpower according to said activation signal; after said power supplyprovides said output power, a confirmation signal is produced; saidtesting module draws said output power according to said confirmationsignal and a set value for producing said limiting level; and the levelof said output power provided to said testing module by said powersupply corresponds to said set value.
 10. The automatic adjusting deviceas claimed in claim 9, wherein said power supply provides a supply powerto said control module according to said input power for providing thepower required by said control module for producing said activationsignal.
 11. The automatic adjusting device as claimed in claim 9,wherein said automatic adjusting circuit includes an adjusting unitcontrolled by said activation signal said confirmation signal, saidadjusting unit produces an adjusting signal according to said comparisonsignal for controlling said programmable signal generating unit toadjust said protection level.